Gasoline antioxidant



Patented Aug. 13, 1940 UNITED STATES GASOLINE ANTIOXIDANT John W. Teter,Chicago, 111., assignor to Sinclair Refining Company, New York, N. Y., a

corporation of Maine No Drawing. Application August 1'], 1937, SerialNo. 159,502

11 Claims.

This invention relates to antioxidants for gasoline and moreparticularly to the use of a mixture of certain compounds for inhibitingthe oxidation of gasoline as well as to the gasoline in which such amixture is incorporated. In its more specific aspect, the inventionrelates to the incorporation in cracked and polymer gasolines of apartially nitrosated mixture of substituted phenolic compounds.

Cracked gasclines and particularly polymer gasolines contain substantialquantities of unsaturated compounds such as olefins. It is well knownthat unsaturated compounds have a tendency to oxidize when the gasolinecontaining them is allowed to stand for an appreciable length of timeafter its production. There are two salient disadvantages 'whichcharacterize the oxidation or deterioration of cracked and polymergasolines originally containing substantial amounts of unsaturatedcompounds. Firstly, gum-like products are formed upon oxidation of theseunsaturated compounds. Such solid products may be formed while thegasoline is in storage tanks with the result that the gasoline has acloudy appearance due to the precipitation of this solid matter. Thegum-like product together with additional solid matter formed in thegasoline tank of an automobile, for example, tends to settle out in thegasoline lines and carburetor of the automobile engine. Secondly, thepresence of the unsaturated compounds in the gasoline imparts to thegasoline a high-antiknoek rating which is higher in gasolinescontaining. the larger quantity of these unsaturated compounds. However,when these unsaturated compounds are destroyed by oxidation theantiknock characteristic of the gasoline is seriously lowered.

For these two well recognized reasons therev have been incorporated incracked and polymer gasolines substances which have the property ofeffectively inhibiting the oxidation of unsaturated compounds in thegasoline. Besides having this requisite inhibitory effect it is alsodesirable that the gasoline antioxidants be substantially insoluble inwater and highly soluble in the gasoline so that there will be notendency for the antioxidant to be dissolved out of the gasoline duringstorage by any moisture in the gasoline.

I have found that a partially nitrosated mixture of substituted phenoliccompounds meets the several requirements of a highly desirable gasolineantioxidant. When a small quantity of this mixture is incorporated incracked or polymer gasoline it exhibits a powerful inhibitory actionwith respect to oxidation of unsaturated compounds contained in thegasolines. Such a mixture is further characterized by a low solubilityin water with ready solubilty in gasoline.

More particularly the novel gasoline antioxidant of my inventioncomprises a partially nitrosated mixture of coal-tar acids having aboiling range between 200 to 216 C. and comprising cresols, xylenols,etc. This mixture of coal-tar acids having the above characteristicswill be referred to hereinafter as lower xylenols.

The lower xylenols mixture may be'nitrosated by subjecting the mixtureto the action of sodium nitrite and a mineral acid such, for example, assulphuric acid. A highly eflicient and inexpensive method of partiallynitrosating such a mixture is fully described in my copendingapplication Serial No. 147,870, filed June 12, 1937. This partialnitrosation efiects nitrosation of the most reactive compound orcompounds in the mixture, and the nitrosated compound or compounds hasthe property of being a powerful oxidation inhibitor for gasoline.Inasmuch as the lower xylenols mixture is a comparatively inexpensivesource of substituted phenolic compounds, the partially nitrosatedmixture is much less expensive than other successful inhibitors now incom- Table I Theoretical Actual ni- Efl'lciency nitrosation trosation ofproduct Percent Percent Percent The inhibitor efliciencies of thepartially nitrosated lower xylenols mixture noted in Table I werecalculated from the percent of nitrosated substituted phenolic compoundsin the mixture determined by analysis of this mixture, the percent ofunreacted compounds in the mixture, and the total determined inhibitorefliciencies of these nitrosated and unreacted compounds as well as thepartially nitrosated mixture considered as a single inhibitor. It willbe readily apparent upon consideration of this table that optimumresults are obtained with a mixture which has been nitrosated to theextent of approximately 40% "theoretical nitrosation.

The inhibitor efilciencies of the nitrosated substituted phenoliccompounds in the mixture as well as the efliciency of the mixture itselfin the foregoing table were determined by the so-called oxygen bomb teston a typical Mid-Continent cracked distillate as the standard ofcomparison. Samples of the untreated gasolines and of the same gasolinein which small quantities of the various antioxidant mixtures wereincorporated were tested for their total induction period. The oxygenbomb test in each case was carried out by placing a 200 c. 0. sample ofthe gasoline to be tested in a suitable container and then placing thecontainer in a pressure bomb. After sweeping the atmosphere within thesealed bomb with oxygen, the bomb was filled with oxygen at a pressureof lbs. per square inch. The bomb was then placed in a steam bath,heated to 212 F., and maintained at this temperature throughout the testperiod. The maximum pressure within the bomb was recorded when thetemperature thereof reached 212 F. The end of the induction period, thatis the point at which the gasoline begins to oxidize, is indicated by adefinite and continued drop in the oxygen pressure within the bomb. Bynoting the time at which this maximum pressure was obtained and the timeat which the first appreciable drop in pressure occurred while thecontents of the bomb were maintained at 212 R, an induction period wasobserved which comprises a direct measure of the relative tendency ofthe various gasoline samples to oxidize during storage.

A small proportion of the novel antioxidant of my invention produces amarked inhibitory effect in gasolines having a tendency to oxidize. Forexample, the incorporation of 7.8 lbs. of a "lower xylenols" mixturenitrosated to the extent of substantially 40% theoretical nitrosation inabout 1,000 barrels (of 42 gallons) of a gasoline having an inductionperiod of 2.0 hours increased the induction period of this gasoline to6.0 hours in the oxygen bomb tests. The effectiveness of thisantioxidant, together with its ready solubility in gasoline, has thesalient advantage of markedly inhibiting the oxidation of gasolines andalso of dissolving in the gasoline without leaving an insoluble residuetherein. The small quantity of this mixture which may be used witheffective results has the further advantage of inhibiting oxidationwithout seriously affecting the colorof the gasoline and withoutimparting an objectionable odor to the gasoline by the incorporationtherein of this novel inhibitor.

The high efficiency of the novel antioxidant of my invention has thefurther advantage of lowering the cost index of the inhibitor below thatof the inhibitors now in commercial use. The cost indices of a lowerxylenols mixture nitrosated to the extent of substantially 40%theoretical nitrosation, as compared with two of the most successfulcommercial oxidation inhibitors now being used, are shown in Table 11together with the amount of each inhibitor which must be added to 1000barrels (of 42 gallons) of a typical Mid-Continent gasoline to raise itsinduction period from 2.0 to 6.0 hours.

The cost index of each inhibitor recorded in Table II was obtained bydividing the cost per unit efficiency of any inhibitor by the cost perunit efllciency of commercial inhibitor "A when each of the inhibitorsis used in the same sample of gasoline in such a quantity as to producea fuel of the same storage stability. The relative cost indices arecompared in this table by arbitrarily setting the cost index ofcommercial inhibitor A at 100. It should be noted in Table II that thecost index of the lower xylenols mixture nitrosated to the extent ofsubstantially 40% theoretical nitrosation is only 47 as compared with100 and 84 for the two commercial inhibitors. This low cost index iscogent evidence of the advantages to be gained by the use of theinhibitor of my invention.

The novel antioxidant of my invention may be readily incorporated incracked and polymer gasolines merely by addition of the inhibitor to thegasoline. The relatively high solubility of the unreacted substitutedphenolic compounds in the mixture in which the nitrosated compound isdissolved aids in the solution of the nitrosated compounds in thegasoline. For example, a mixture of the antioxidant with some of thegasoline to be treated may be added to a stream of the gasoline as thelatter is pumped into a storage tank. In such a case, the rate ofaddition of the mixture to the stream may be reduced with particularadvantage to a rate substantially below that which will give a saturatedsolution of the antioxidant in the stream before the stream reaches thestorage tank. Alternatively, the mixture may be introduced slowly intothe low pressure side of a circulating pump associated with the gasolinestorage tank, or may be incorporated in the gasoline at the same time,for example, that tetra-ethyl-lead is added to the gasoline. Theinhibitors, on the other hand, may be incorporated in the gasoline withadvantage by dissolving the inhibitor in a suitable solvent inert withrespect to any effect upon the gasoline or the inhibitor. These inertsolvents may comprise aliphatic or cyclic alcohols such, for example, asmethyl alcohol, ethyl alcohol, butyl alcohol, iso-propyl alcohol, orcyclohexanol. Thus, a concentrated solution of the inhibitor in anappropriate solvent may be prepared and added to the gasoline to betreated.

.As a further alternative, the inhibitor may be incorporated in thegasoline with advantage by dissolving the inhibitor in naphtha or othersuitable solvent and subsequently adding the solution to the fuel to bestabilized. This naphtha solution of the partially nitrosated mixturemay be obtained directly as the final product in the preparation of thepartially nitrosated mixture wherein naphtha, or other suitable solvent,is used for extracting the partially nitrosated mixture from the aqueousreaction solution of the mixture. The solubility of the inhibitor of myinvention appears to increase noticeably with an increase in thetemperature of the naphtha in which the inhibitor is dissolved. Thus, aconcentrated solution of the inhibitor may be readily obtained bydissolving a substantial quantity of the inhibitor in a heated naphtha,or by some equivalent means.

The quantity of the novel antioxidant of my invention which may be usedwith advantage should not be limited to the quantity used in theforegoing illustrations. The optimum amount of antioxidant which shouldbe used in each case will vary with the characteristics of the gasolineto be treated and will be readily ascertainable by simple tests on thegasoline by one skilled in the art.

I claim:

1. The method of inhibiting the oxidation of gasoline which comprisesincorporating in the gasoline an effective amount of a partiallynitrosated mixture of substituted phenolic compounds comprising readilynitrosatable phenolic compounds and relatively diflicultly nitrosatablephenolic compounds in which mixture substantially only the readilynitrosatable phenolic compounds are substantially completely nitrosated.

.the range of 200 to 216 C. nitrosated to the extent of substantially40% theoretical nitrosation of the nitrosatable compounds in themixture. v

4. An improved motor fuel which comprises gasoline containing aneffective amount of a partially nitrosated mixture of substitutedphenolic compounds comprising readily nitrosatable phenoliccompounds'and relatively difilcultly ultrosatable phenolic compounds inwhich mixture substantially only the readily nitrosatable phenoliccompounds are substantially completely nitrosated.

5. An improved motor fuel which comprises 5 gasoline containing aneffective amount of a mixture ofvsubstituted phenolic compoundsnitrosated to the extent of between substantially. 25% to 40%theoretical nitrosation of the nitrosatable compounds in the mixture.

6. An improved motor fuel which comprises gasoline containing anefiective amount of a mixture of coal-tar acids boiling within the rangeof 200 to 216 C. nitrosated to the extent of substantially 40%theoretical nitrosation of 1 the nitrosatable compounds in the mixture.

7. An improved motor fuel which comprises gasoline containing anefiective amount of a mixture of coal-tar acids boiling within the rangeof 200 to 216 C. nitrosated to the extent an of substantially totheoretical nitrosation of the nitrosatable compounds in the mixture.

8. An oxidation inhibitor for gasoline whic comprises a partiallynitrosated mixture of substituted phenolic compounds comprising readilynitrosatable phenolic compounds and relatively difllcultly nitrosatablephenolic compounds in which mixture substantially only the readilynitrosatable phenolic compounds are substantially completely nitrosated.

9. An oxidation inhibitor for gasoline which comprises a mixture ofsubstituted phenolic compounds nitrosated to the extent of substantially25% to 40% theoretical nitrosation of the nitrosatable compounds in themixture.

10. An oxidation inhibitor for gasoline which comprises a mixture ofcoal-tar acids boiling within the range of 200 to 216 C. nitrosated tothe extent of substantially 25% to 40% theo- 40 C. nitrosated to

